In operator vehicles such as earth-moving machines or agricultural machines, there is normally a hydraulic fluid supply circuit, the fluid being hydraulic oil, comprised in a main tank. The main tank is typically constituted by the motor casing and/or the gear box. A first constant-flow pump takes oil from the main tank. A second variable-flow pump is connected in aspiration with the delivery of the first pump. The second pump is predisposed to supply the oil to one or more hydraulic distributors which are connected in outlet to one or more actuators.
The first pump also supplies a lubrication circuit, predisposed to send oil to various zones of the operator vehicle with the aim of lubricating various organs of the operator vehicle. The lubrication circuit is connected in inlet to an intermediate point between the first pump and the second pump, while it is connected in discharge to the main tank. An auxiliary conduit, provided with a check valve, is arranged in parallel with the lubrication circuit.
The supply circuit functions as follows. The first pump continuously develops a constant flow of oil which is divided between the lubrication circuit and the second pump, which second pump supplies the oil to the distributors. During the working stages of the vehicle, in which the activation of the actuator is not required, all the oil flow developed by the first pump is directed towards the lubrication system. This flow, which considerably exceeds the flow required by the lubrication circuit, flows in part back through the auxiliary conduit, and the relative check valve, to the main tank. During the working stages, in which the activation of the actuators is required, a part of the oil flow developed by the first pump is directed, by means of the second pump, to the hydraulic distributors.
The quantity of oil present overall in the vehicle supply circuit must be sufficient to enable both lubrication of the vehicle and all the parts requiring lubrication, as well as activation of the actuators on board the vehicle. This is therefore a not insignificant amount of oil, which occupies a certain volume of the main tank. As already mentioned herein above, the main tank of the supply circuit is constituted generally by the engine casing and/or the gear box. The drive shaft and the vehicle gear box are therefore immersed in an abundant quantity of oil, rotation of shafts and gears represents a significant element for energy dissipation.
The aim of the present invention is to provide a control device of an oil level in a main tank of a supply circuit which limits the quantity of oil present internally of the main tank to what is strictly necessary for the operations which have to be performed at any given time, such that the energy dissipation produced by the agitating of the oil is proportionally reduced.
An advantage of the device of the present invention is that it does not lead to an increase in the space taken up on board the vehicle.
A further advantage of the device is that it can be installed on board vehicles which have not been originally predisposed for the device.